The present invention relates to a treatment apparatus for subjecting a substrate, such as a semiconductor wafer, to specific treatments in given spaces, a treatment method, and an impurity removing apparatus adapted for use with the treatment apparatus.
In a photoresist treatment process of a semi-conductor manufacturing method, for example, a resist film is formed by applying a resist to the surface of a substrate, such as a semiconductor wafer (hereinafter referred to simply as "wafer"), and the substrate is exposed to a given pattern and developed with a developing agent. Conventionally, this series of treatments is carried out by means of a coating/developing apparatus in which individual treatment units are arranged intensively and systematized.
Usually, the coating/developing apparatus comprises a plurality of treatment units. These treatment units include, for example, a treatment unit for an adhesion treatment for improving the grab of the resist, a resist treatment for applying the resist, a heat-treatment unit for keeping the exposed substrate in an atmosphere of a given temperature, and a developing unit for developing the exposed substrate with the developing agent. The substrate or wafer is loaded into or unloaded from these individual treatment units for specific treatments by means of a transportation mechanism such as a transfer arm.
Since the treatments require a clean atmosphere, the coating/developing apparatus is set in a clean room, and regions around or over the apparatus are surrounded by suitable panels. Provided in the upper portion of the apparatus is a cleaned air supply unit, such as the so-called fan-filter unit (FFU) that integrally combines a fan and a filter. The treatment units are located under down flows of cleaned air from the FFU. In order to remove alkaline components, such as ammonia, in the atmosphere in the coating/developing apparatus, a chemical filter is disposed independently on the upper-stream side of the FFU.
As modern semiconductor devices become more highly integrated, the line widths of patterns become finer and finer. To cope with this, the resist is formed of a material capable of chemical amplification. If this resist material reacts with ammonia in the atmosphere, however, a slightly soluble or insoluble neutralized layer is inevitably formed on the surface of the substrate, adversely affecting subsequent treatments. Accordingly, the ammonia and other alkaline components in the atmosphere in the coating/developing apparatus must be minimized in quantity. The formation of the neutralized layer can be prevented by restricting the quantity of the alkaline components to, for example, 1 ppb or less.
The life performance of the so-called chemical filter set in the conventional coating/developing apparatus depends on the humidity in the system, the quantity of alkaline components, and the flow rate (per unit time) of air passing through the chemical filter. Therefore, the time for the replacement of the chemical filter cannot be predicted with ease, and the replacement requires the whole system to be stopped, resulting in reduction in throughput. Besides, the chemical filter is expensive, so that the running costs are increased.
Accordingly, the inventors hereof attempted to remove alkaline components in an atmosphere by means of the so-called gas-liquid contact with an impurity remover instead of using the chemical filter.
If impurities, such as alkaline components, contained by the atmosphere in the coating/developing apparatus are removed simply by the gas-liquid contact, however, they cannot enjoy high removal efficiency. In the case where the impurity concentration of the atmosphere is high, the impurities cannot be easily removed to the degree high enough to maintain the appropriate cleanness of the atmosphere in the systematized apparatus. Further, the impurity remover, e.g., pure water, which is used for the gas-liquid contact, entails a nonnegligible running cost.
In the case where pure water is used as the impurity remover, for example, microorganisms, such as sundry germs, algae, etc., may possibly multiply if the water is circulated. These multiplied microorganisms cause clogging of piping in a circulation system, degeneration of the impurity remover itself, etc. Accordingly, the impurity removing capacity of the remover is lowered, so that suitable atmospheres cannot be maintained in given spaces in the treatment apparatus. Thus, it is necessary periodically to discharge the entire impurity remover from the apparatus and disassemble and clean associated devices, and in some cases, to replace some components. During periodic cleaning operation for an impurity removing apparatus, moreover, the treatment apparatus, as well as the removing apparatus, must be stopped, and the throughput is lowered also for this reason.